1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to the improvement of a dimple pattern of a golf ball.
2. Description of the Related Art
Golf balls have a large number of dimples on their surfaces. A role of the dimples involves causing turbulent flow separation through promoting the transition of a turbulent flow of a boundary layer by disrupting the air flow around the golf ball during flight. By promoting the transition of a turbulent flow, separation points of air from the golf ball shift backwards leading to the reduction of a drag coefficient (Cd) so that a flight distance of the golf ball is prolonged. In addition, difference of separation points on the upper and lower sides of the golf ball resulting from back spin is increased by the promotion of the transition of a turbulent flow, therefore, lift force that acts on the golf ball is elevated.
Various golf balls that are provided with an improved dimple pattern to which the improvement of the flight performance is intended have been proposed. For example, JP-B-50744/1983 discloses a golf ball having dimples densely arranged so that pitches between the dimples be equal to or less than 1.62 mm as much as possible. Further, JP-A-192181/1987 discloses a golf ball having dimples densely arranged so that new dimples can not be formed having an area greater than the average area, on the land parts that are parts other than the dimples. Moreover, JP-A-347177/1992 discloses a golf ball having dimples significantly densely arranged so that number of the land parts on which a rectangle having a predetermined size can be depicted be equal to or less than 40.
Any of the golf balls disclosed in these known literatures has dimples that are densely arranged. In other words, they have an increased surface are a occupation ratio of the dimples. One skilled in the art acknowledges that a critical factor that influences on effects of the dimples is the surface area occupation ratio.
However, the surface area occupation ratio is not necessarily only one index for supeculating the effects of the dimple. From another aspect in addition to the surface area occupation ratio, there still exists room to study on the amelioration intending to further improvement of the flight performance.